Radio frequency identification (RFID) systems are used for a variety of different applications. As one example, RFID systems are commonly used to track and monitor shipping containers or other mobile assets. RFID tags are attached to the shipping containers or other assets, and exchange wireless communications with other system components, including stationary interrogators and/or readers.
Over time, RFID tags are being provided with a progressively increasing degree of extended functionality, above and beyond that needed for basic RFID operation. These optional extended functions are sometimes referred to as “extended services”. As one aspect of this, extended services may be implemented by adding supplemental hardware and/or software components to a tag. For example, a tag may include one or more sensors, along with a software module that handles the sensors. As another example, a tag may include a global positioning system (GPS) receiver, along with a software module that processes data from the GPS receiver. As yet another example, a tag may include a software module that provides enhanced security for wireless communications, by encrypting and decrypting information being sent and received by the tag.
Many RFID tags and interrogators are currently being manufactured to communicate according to a protocol that is an international standard commonly known as ISO 18000-7. Although this protocol has been generally adequate for its intended purposes, it has not been entirely satisfactory in all respects. As one example, this protocol does not allow an interrogator to efficiently obtain from a given tag an identification of all the extended services that are implemented on the tag.
A further consideration is that there are industry-standard protocols that can be used to interact with a single sensor. One example is ISO 21451.7, which is based on another industry-standard protocol commonly know as IEEE 1451.7. Although the ISO 21451.7 protocol has been generally adequate for its intended purposes, it has not been entirely satisfactory in all respects. As one aspect of this, there is currently no convenient way to use this protocol in conjunction with the ISO 18000-7 protocol, so that an interrogator can directly and efficiently communicate with a sensor that is provided in a tag. As another aspect, the ISO 21451.7 protocol is specifically designed for interaction with only a single sensor. Thus, in addition to the fact that there is currently no way to use the ISO 21451.7 protocol in conjunction with the ISO 18000-7 protocol, where a tag has multiple sensors it would be necessary for the tag to be simultaneously running several separate, identical instantiations of a single-sensor software module for ISO 21451.7 (one module for each sensor). This would obviously be very cumbersome and inefficient.